1. Field of the Invention
The present invention relates to an antiferroelectric liquid crystal composition suitable for use in liquid crystal display elements that utilize the response of antiferroelectric liquid crystal to an electric field.
2. Description of the Related Art
Recently, liquid crystal displays have become useful as display elements in a wide range of applications which take advantage of their characteristics such as thin form, light weight and low power consumption. The majority of these display devices are typically of the TN (twisted nematic) type that use nematic liquid crystal. Since the driving of this TN type of display is based on the anisotropy of the relative dielectric constant of the liquid crystal, its response speed is slow thereby resulting in a need for improvement.
In contrast, liquid crystal devices using chiralsmectic C (S.sub.C *) liquid crystal, which were discovered by Meyer, et al., exhibit ferroelectric properties, have high-speed response and memory capabilities which cannot be achieved by nematic liquid crystals. Research has been conducted to apply this liquid crystal to ferroelectric liquid crystal displays by taking advantage of these characteristics. It has been difficult, however, to realize the favorable orientation and memory capabilities offered by this display method in actual cells. There are also numerous problems yet to be solved, including the problem of susceptibility to external shock.
On the other hand, an antiferroelectric phase (S.sub.CA * phase), discovered by Chandani, et al., exhibits three stable states on the low temperature side of the above-mentioned S.sub.C * phase. This antiferroelectric liquid crystal exhibits a thermodynamically stable phase in which dipoles are arranged in antiparallel fashion for each adjacent layer. It causes a magnetic field-induced phase shift between the antiferroelectric phase and ferroelectric phase that is characterized by a well-defined threshold value relative to the applied voltage and double hysteresis properties. Studies are being conducted on a novel display method that uses this switching behavior.
In the case of applying an antiferroelectric liquid crystal to display elements, conventionally known ferroelectric liquid crystal materials cannot always be said to be preferable in terms of the liquid crystal temperature range over which a ferroelectric phase is demonstrated, the threshold voltage for driving, display performance and so forth. In consideration of these circumstances, the object of the present invention is to provide an antiferroelectric liquid crystal composition having an improved liquid crystal temperature range, threshold voltage and display performance.